<?php
$a = 15;
$b = 27;
echo "<br>交换前的数字为：<br>";
echo "a =".$a."且 b=".$b;
$temp = $a;
$a = $b;
$b = $temp;
$b = $temp;
echo "<br>交换后的数字为：<br>";
echo "a =".$a."且 b=".$b."<br>";